Despa Valley is the first of seven areas that make up the Valley of Doom, and it is also the smallest. It is a 3x3 block of screens in the southeast corner of the map where you will find no unique items. You will find a life potion as well as a bible here, however.
Life Potions are, as you might expect, vital to your survival. Unlike potions in many other games, they don't restore your life; rather, they permanently increase it by one life bar (7 hit points) per potion. You start with one reserve Life Potion, and there are 18 more that you can buy in the valley. (The game can only display 18 of these potions, and some strange but useful things happen if you should obtain The 19th Life Potion.)
Bibles, on the other hand, allow you to carry more money. Don't ask me why. You start off with the ability to carry 1,000 gold, and each Bible will increase your Maximum Gold. It is a good idea to track down and purchase every Bible in an area before you face the boss, because your gold is filled to its maximum any time you defeat a boss. (Keep in mind that you can only face each boss once.)
With that in mind, your first goal should be to earn money and buy the Bible and Life Potion available in Despa Valley. They cost 500 gold each, and can be found in caves in the northwest and northeast corners of the area, respectively. You'll have to defeat at least two Red Snakes to open the cave where the wise woman is selling the Bible.
You earn money by defeating enemies, and different enemies drop different amounts of gold. Orange Bees drop by far the most gold of any enemy in Despa Valley (100 gold per kill), but they can be difficult to fight. They fire projectiles you need to avoid, and fly in a circular pattern, often over terrain you can't pass. It is safer to earn money fighting Blue Snakes in the center of the area. They have 2 hit points, but will go down with a single sustained sword strike. All types of snakes move slowly, but occasionally they will jump. For this reason, it is a good idea to fight them from the sides whenever possible.
In addition to selling things, the inhabitants of the many caves of Golvellius can provide hints or other services. There is exactly one cave hidden on every screen in the game except the one you start in. Some caves, including most in Despa Valley, are already open when you enter a screen. Others have to be unlocked by various other means. For example, the northern and eastern screens have caves which will only appear after you've defeated at least one enemy. The fairy Rio can be found in many locations, but her hint in the northern screen should lead you towards Despa Cave.
There is one other cave of note in Despa Valley: you'll find Randar in the southwest corner of the area. Randar will restore all of your lost life for the sum of 150 gold. He is your only sure source of healing at the moment, so don't hesitate to pay him a visit if you need to.
Despa Cave
The most dangerous screen in Despa Valley is, unsurprisingly, the one that contains the dungeon where Despa hides. You'll find both Orange Bees and Blue Snakes outside. You'll have to defeat one enemy to open the dungeon entrance, but it doesn't matter which type it is. Once it is open, head to the dungeon entrance to escape the enemy barrage.
Unlike the Introductory Dungeon, Despa Cave is a vertically-scrolling dungeon. You also need to be careful, because if you move all the way to the bottom of the screen, you will be forced out of the dungeon and have to start over from the beginning. Enemies don't push you in vertically-scrolling dungeons, but it is easy to get caught behind walls. Kelesis's forward movement is very slow in these dungeons, but he can move quickly to the sides, so it is usually best to stay as high up on the screen as you dare.
The dungeon starts off devoid of enemies. You'll follow a winding path that will give you a good introduction to how Kelesis moves in vertically-scrolling dungeons. Eventually Blue Bats will start to attack. Avoid or destroy them at your discretion. (Remember that defeating the boss will fill up your gold, so it isn't generally worth fighting enemies in dungeons for the loot.) The path branches at this point, but both branches will converge on the left side.
You'll soon come to an area where three paths repeatedly branch and converge. There are no dead ends, so don't worry about which path to take. What you should worry about is the Giant Bat that appears at the end of the area. Similar to the Giant Snakes that you will find in side-scrolling dungeons, Giant Bats will drop a large number of healing tokens when defeated. However, they will not stand still, and there is no guarantee that you will defeat them before the end of the dungeon. If you need the health, your best bet is an extremely aggressive approach. You'll take a lot of hits, but the healing will more than make up for it. If your health is relatively high, it might be better to hang back, but take care not to hang so far back that you end up being forced out of the dungeon!
Soon enough you will enter Despa's room. The boss can take a lot of hits, but he doesn't dish out much damage. If you bought the Life Potion and came in at full health, you can survive about 10 of Despa's attacks. The fight will take a while, though, so you'll want to avoid as many attacks as you can.
Despa's pattern is very simple: he walks back and forth, occasionally throwing what appear to be snowflakes towards the bottom of the screen. Because he never moves vertically, you can safely attack him from below without worrying about making contact. You'll still need to be ready to dodge the snowflakes, of course. Keep hitting him and eventually he will fall, giving you a whole lot of money in the process.
Your time in Despa Valley is almost over, but there is still one more thing to do. Remember the center screen that was filled with Blue Snakes, but had no cave? With Despa's defeat, a cave has now opened there. A wise woman will sell you one of the seven Crystals for the hefty sum of 1,000 gold. You won't actually need any of the crystals until the end of the game, so you can save your money if you're so inclined, but 1,000 gold is not hard to make up. If nothing else, it will save you the trip back here later in the game.
Crystal in hand, it's time to leave the area. In addition to the new cave, defeating Despa opened up a path to the north, leading to Rolick Desert. That's your next destination.